This invention relates to jet drop recorders of the general type disclosed in U.S. Pat. Nos. 3,577,198, 3,701,476, 3,701,998, 3,709,432, 3,739,393, 3,882,508, 3,970,222 and 4,031,561, all assigned to the assignee of the present invention. Such jet drop recorders comprise a series of electric and fluidic components, including an orifice plate and a charge plate, for generating one or more rows of jets of ink and selectively charging the ink droplets as they form from the jets. Typically, there may be several hundred jets formed in each such row, and each jet may be stimulated to produce drops of ink at a rate of about 400 kHz. All such drops fall through an electrical deflection field, and those which are charged are deflected into a catcher. Uncharged drops are deposited on a moving web transported below the recording head.
One of the critical requirements in such a jet drop recorder is an orifice plate which will produce several hundred jets of ink which are precisely positioned, precisely parallel, and precisely uniform. The orifice plate must also be compatible with the ink compositions used, and must be resistant to erosion by the ink. In addition, the regions around the orifices should be sufficiently open to provide for cleaning ink and dirt deposits from the orifices for maintaining proper operation.
One method for producing such an orifice plate is to etch a suitable substrate, which can be done using well-known photoresist techniques. A difficulty with this method, however, is the requirement of virtually absolute uniformity among all the orifices. When a metallic substrate is etched, for example, great care must be taken to achieve the required accuracy.
Some success in the forming of etched orifice plates has been achieved through the use of selective etching of crystalline substrates along particular planes of the crystal. See, for example, U.S. Pat. Nos. 3,921,916, 3,949,410, and 4,007,464. However, the preferred crystalline material (silicon) does not have as much resistance to erosion by the ink as would be desirable, sometimes requiring an erosion resistant coating as shown in several of these references. Such crystalline orifice plates are thus expensive (being made of a single crystal), difficult and expensive to fabricate, and not always of the desired strength or durability.
A need thus remains for an orifice plate which meets the above noted requirements in an inexpensive, easily fabricated, strong, durable, and reliable configuration.